Blood Groups - Cat

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Cats and dogs have very different blood grouping systems. Cats have an A-B blood group system and inherit blood types as a simple dominant trait where A is dominant over B.

Cats have three blood groups: Group A, B or AB. Group A which can be either A/A or A/B is the most common blood type of domestic short and long haired cats in the UK. Group B which is always B/B is very common in Devon Rex, Persians, British Shorthair, Somali, Himalayan and Birman breeds. Rarely cats can also be group AB.


Both the blood donor and recipient should always be blood typed prior to transfusion. This is especially important in cats due to the occurrence of alloantibodies. Commercial in house kits are convenient or reference laboratories often provide blood typing services.

Group A cats have low titres of anti-B antibodies hence giving group A cats group B blood will cause destruction of red blood cells and a mild transfusion reaction.

Group B cats have high titres of anti-A antibodies and giving group B cats type A blood can result in a potentially fatal transfusion reaction. Type AB cats do not have anti A or B alloantibodies and can receive type A/B or A blood.

Blood group incompatilibility in Cats

Donor Group Recipient group Transfusion reaction
A A None
B B None
B A Slight
A B Potentially fatal
AB AB None
A AB None

Additionally neonatal isoerythrolysis can occur due to the presence of naturally occuring alloantibodies in kittens born to queens who have a different blood type. The kittens are born healthy but following their first suckle will suffer from anaemia and jaundice which can rapidly progress to death.

Simplified compatibility tests

Time is needed to determine full compatibility between the donor and recipient. This is not always possible in the emergency situation and in these cases it is possible to undertake simplified compatibility tests. These tests can be performed in minutes however are much less reliable.

They involve centrifuging 0.5mls of the donors blood and 0.5mls of the recipient blood in EDTA tubes hence separating red blood cells and plasma. Various amounts (as below) are then added together and blood smears are prepared and examined microscopically.

Three tests need to be undertaken:

1) The major test where 3 drops of plasma from the recipient and one drop of red blood cells from the donor are added together left for 1-3 minutes and then examined microscopically. If this reaction shows there is agglutination the transfusion should not be performed.

2) Minor test where 3 drops of donor plasma is added to 1 drop of recipient red blood cells. If agglutination occurs then transfusion can occur but with constant monitoring of the patient.

3) A control reaction must also be carried out with 3 drops of donor plasma and 1 drop of donor red blood cells. If agglutination occurs then there is an error and the test must be repeated.

See also: Indications for Blood Transfusions
Administering a Blood Transfusion
Blood Groups
Blood Products
Blood Groups - Dog


Transfusion Therapy. Lymphoreticular and Haematology module. 4th year notes. Royal Veterinary College London. 2009.

Selected Topics in Canine and Feline Emergency Medicine. Volume 1. Handbook for the veterinary practitioner. Royal Canin.